This is a common design - and it's bad.

Insulating the pipes will help some, but they will still cool down after about 20 minutes.

Are you using a manifold system where each faucet makes a home run - or a branch system where there is one hot water line running to the master bath and it branches off? (a photo would be really helpful).

Make sure the hot water line(s) are not over-sized. Oversized lines take a lot more water to flush out before hot water gets to where it's going.

Insulating the hot water pipes is easy. Get the split foam and a pair of scissors and cut the pipe insulation to go between the anchor points. You can probably even just go over the anchors and use zip ties to hold the insulation closed around the anchors.

Ultimately you may need a circulating pump to keep the hot water in the lines. I like to avoid those because they waste energy. You want to have a dedicated return line AND you want to insulate the hot water pipes and return line if you go that route.

It's a single straight run (brand new remodeled bathroom) from WH to master bath. I am thinking when the WH wears out I will install an instant hot WH type. I just hate wasting all that water waiting for it to warm up. I started using the foam pipe insulation but its tedious and exhausting.Lying on my back in the crawl space. Yuk. ty for your response!

You can install a 5 gal electric tank heater in the crawl space right below the master bath. Connect it in series with the main water heater so that you get hot water very quickly, then the main heater kicks in.

That sounds like great idea. Any plumber can do that?

Here's an example of a Point of Use heater.

What a great little unit. Never would have thought of such a thing. Thank you. I'll get hold of my contractor and see if he can get a guy to do this for me. Thanks again.